I agree with everything you say @Marshmallowkiss
Plum - what do you want? He's not going to change back. This is who he is. And you're unhappy, aren't you?
What people who fall 'in love' don't seem to understand is that for the first 6 months, even I'd say the first year, you see the filtered, best behaviour version of the person you meet. It's the very best they will ever be at the start because they want you and they want to be loved by you so they put the best version forward. It's human to want to build connection and feel like you belong somewhere so we adapt and try to flex a bit to make that connection grow.
But often people get caught up in the initial feeling of love and acceptance in that early 'best behaviour' version which isn't really the real person.
Then they keep hoping that best version is still available. It's not. It was never real. It was a filtered, sanitised version to try to form a connection but it's not who they really are. That comes further down the line in year 2 or more... You need to be pragmatic, not emotional and weight up probabilities I would say.. hard though that is.
I'm not sure we have an answer here where there's a happy outcome.
You stay, you're unhappy. You leave, you're unhappy.
The only thing is if you leave, you will eventually get over him and be free to start a new relationship with someone who actually could make you happy long term, if you choose wisely. Staying doesn't look like it will ever be that but good luck with trying... if that's the path you choose.